Therapeutic agents designed to bind and block the biological activities of tumor necrosis factor-alpha (TNFa) have been shown to be effective in the treatment of rheumatoid arthritis (RA). Two anti-TNFa agents are currently marketed for the treatment of RA; etanercept (Enbrel®) and infliximab (REMICADE®). Clinical trials have shown that both of these agents rapidly improve signs and symptoms associated with RA in the majority of patients. Moreover, they slow, and may even arrest or improve, the joint structural damage that accompanies RA.